Asteroid belt

The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids or minor planets. The identified objects are of many sizes, but much smaller than planets, and, on average, are about one million kilometers (or six hundred thousand miles) apart. This asteroid belt is also called the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System. The asteroid belt is the innermost and smallest circumstellar disc in the Solar System. Its total mass is estimated to be 3% that of the Moon, with about 60% contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. Classes of small Solar System bodies in other regions are the near-Earth objects, the centaurs, trojans, and the trans-Neptunian objects (Kuiper belt objects, scattered disc objects, sednoids, and Oort cloud objects.) Ceres, the only object in the asteroid belt large enough to be classified as a dwarf planet, is about 950 km in diameter, whereas Vesta, Pallas, and Hygiea have mean diameters less than 600 km. The remaining mineralogically classified bodies range in size down to a few metres. The asteroid material is so thinly distributed that numerous uncrewed spacecraft have traversed it without incident. Nonetheless, collisions between large asteroids occur and can produce an asteroid family, whose members have similar orbital characteristics and compositions. Individual asteroids within the belt are categorized by their spectra, with most falling into three basic groups: carbonaceous (C-type), silicate (S-type), and X-type, which includes metal-rich asteroids. The asteroid belt formed from the primordial solar nebula as a group of planetesimals, the smaller precursors of the protoplanets. However, gravitational perturbations from Mars...